1. Field of the Invention
The present invention relates to devices and methods for determining correlation maxima, which are useable, in particular, for digital transmission systems.
2. Description of Prior Art
For a receiver in a digital transmission system to be able to synchronize to a digital signal sent out by a transmitter, the transmitter radiates a digital signal known to the receiver. The receiver's task is to determine the precise time of arrival (TOA) of the signal sent. To determine the time of arrival, the cross-correlation between the digital receive signal and the known digital transmit signal is calculated. Subsequently, the magnitude maximum of the cross-correlation is detected, and the time of arrival of the transmit signal is determined from the position of the correlation magnitude maximum.
If a correlation magnitude maximum is to be searched for in a predefined range of correlation magnitude values and/or in a predefined range of indices 1 of a correlation signal, the correlation magnitude maximum may be determined by determining the maximum of all correlation magnitudes present within the predefined range.
However, if a correlation magnitude maximum is to be searched for across a continuous signal, i.e. across a stream of samples, assessments must be made continuously as to whether or not the correlation magnitude that has just been calculated represents a valid local maximum. To determine such a local maximum, a specified threshold value may be used along with the rule that a correlation magnitude maximum is at hand when a correlation magnitude to be assessed exceeds the threshold value. However, such a method is not flexible and imprecise since it offers no possibility of adjustment to a changing transmission channel. Thereby, the determination of the correlation magnitude maximum may be flawed. As a result of a flawed determination of the correlation magnitude maximum, a synchronization between a transmitter and a receiver of a transmission system is not possible, or there may be flawed data transmission.